from collections import deque

WINDOW_LEN = 18

state = 0 # waiting state is start state

aud_bal = 10000.0
btc_bal = 0.0

historic_prices = deque(maxlen=WINDOW_LEN)

BUY_CONSTANT = 0.95
SELL_CONSTANT = 1.05
SAFETY_CONSTANT = 0.80

def BuyBitcoin(aud_bal, buy_price):
    """

    :param aud_bal: AUD to spend
    :param buy_price: Price of 1 BTC
    :return:
    """
    print "Bought {} AUD worth of BTC @ {} ({} total BTC)".format(aud_bal, buy_price, aud_bal / buy_price)
    return aud_bal, aud_bal / buy_price

def SellBitcoin(btc_bal, sell_price):
    print "Sold {} BTC worth of AUD @ {} ({} total AUD)".format(btc_bal, sell_price, btc_bal * sell_price)
    return btc_bal * sell_price, btc_bal

import random
random.seed(1)

def GetCurrentPrice():
    return (18000.0 + random.randint(-1000, 1000))

safety_thres = 0.0

# buy/sell relative to program, not exchange
while True:
    btc_aud = GetCurrentPrice()
    print "Fetched {} BTC/AUD, ({} AUD,{} BTC left)".format(btc_aud, aud_bal, btc_bal)
    historic_prices.append(btc_aud)

    # waiting
    if state == 0:
        buy_thres = historic_prices[0] * BUY_CONSTANT
        print "Buy threshold is set @ {}".format(buy_thres)
        if btc_aud < buy_thres and len(historic_prices) == WINDOW_LEN:
            buying_price = btc_aud
            state = 1

    # buying
    if state == 1:
        aud_used, btc_bought = BuyBitcoin(aud_bal, buying_price)
        btc_bal += btc_bought
        aud_bal -= aud_used
        sell_thres = buying_price * SELL_CONSTANT
        print "Sell threshold is set @ {}".format(sell_thres)
        safety_thres = buying_price * SAFETY_CONSTANT
        print "Safety threshold is set @ {}".format(safety_thres)
        state = 2

    # looking for sell
    if state == 2:
        if btc_aud > sell_thres or btc_aud < safety_thres:
            aud_bought, btc_used = SellBitcoin(btc_bal, btc_aud)
            btc_bal -= btc_used
            aud_bal += aud_bought
            if btc_aud > sell_thres:
                print "Sell threshold was @ {}".format(sell_thres)
                state = 0
            else:
                print "Safety threshold was @ {}".format(safety_thres)
                break